Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $13.99   4.415%   $14.6077   $14.61   $14.60   $14.60  
  Purchase #2 $172.64   7.315%   $185.2686   $185.27   $185.25   $185.30  
  Purchase #3 $16.70   11.610%   $18.6389   $18.64   $18.65   $18.60  
  Purchase #4 $140.92   3.844%   $146.337   $146.34   $146.35   $146.30  
  Purchase #5 $239.57   7.448%   $257.4132   $257.41   $257.40   $257.40  
  Purchase #6 $118.33   4.407%   $123.5448   $123.54   $123.55   $123.50  
  Purchase #7 $203.70   6.162%   $216.252   $216.25   $216.25   $216.30  
  7 purchase totals = $905.85       $962.0622   $962.06   $962.05   $962.00